(1) Field of the Invention
This invention relates in general to a device and method for extracting liquid from a well.
(2) Description of the Related Art
When trying to produce natural gas from a well, often times, liquids from the desired formations are simultaneously produced with the natural gas. The production of this liquid can adversely affect the gas production if the liquid is allowed to build up within the well bore. In the case of an oil well, however, the liquid is the desired component to remove for sale. An example of the production of a liquid from a well is production of water within coal bed methane wells when producing methane.
The liquid produced is typically removed by a pump. The pump can be a submersible, sucker rod, positive displacement or any other type of down-hole pump. Often in the beginning of a coal bed methane well's life, water production is constant, but as the well ages the liquid production is reduced or intermittent therefore limiting the amount of time that the pump must run. If the pump removes all of the water from within the well bore and the pump continues to operate, it adversely affects or more rapidly diminishes the useful life of the pump. The operation of the pump without liquid could cause the pump to burn up or prematurely wear out. In addition to reducing the life or damaging the pump by dry or reduced flow operation, gas is allowed to escape into the liquid production tubing and into water tanks/pits or water/liquid lines. This ultimately leads to the gas being lost into the atmosphere.
One approach to solving the problem would be a human (well tender) programming a timing device to control the pump's on/off cycle. This on and off cycle is simply a human guess on how often the pump should pump or not pump based on pressures, flows, well age, etc. This is largely inaccurate and requires persons to constantly monitor and modify the cycles at each individual well site.
Another approach to solve the problem is to use physical data from the surface equipment to control when the pump turns on/off. However, this can be very difficult or impossible to achieve. These controllers look at the following types of data among others:
(1) how much pressure is on the well bore;
(2) the depth of the well;
(3) the weight of the liquid being lifted;
(4) a load sensor on the pumping unit;
(5) the power consumed by the pumping unit; and/or
(6) the production of the well.
All of these controllers are located on the surface and often times are not reliable.